1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method, and more specifically to an image processing apparatus and an image processing method for removing a noise generated by scanning a foreign object from image data obtained by scanning an original document.
2. Description of the Related Art
In recent years, some scanners, facsimiles, copying machines, and the like are provided with an image scanning apparatus which has a line sensor placed in a fixed manner and formed by a plurality of photoelectric transducers aligned in a main scanning direction and which adopts a scanning mode in that an original document is scanned by the line sensor by conveying the original document in a sub-scanning direction orthogonal to the main scanning direction. This image scanning apparatus is provided with a transparent copyboard between the original document and the line sensor for positioning the conveyed original document in a scanning position. The light reflected by the original document is transmitted through the copyboard and received by the line sensor. Consequently, a problem arises when a foreign object is stuck on the copyboard and the line sensor scans the foreign object instead of the original document, thereby generating a streak of noise in the image data.
Japanese Patent Laying-Open Nos. 2003-198838 and United States Patent Application Publication No.US2003/0090742 describe the technologies for correcting a noise region in the image data obtained by scanning an original document generated due to a foreign object stuck on a copyboard. According to the technology described in Japanese Patent Laying-Open No. 2003-198838, the noise region within the image data is deleted from the image data and interpolated by an image obtained by enlarging a region in the vicinity of the noise region. In the case where the vicinity of the noise region is a region of dots, however, the size of the dots becomes enlarged so that the image quality cannot be enhanced. Moreover, United States Patent Application Publication No.US2003/0090742 describes the technology in which, according to the width of the noise region, pixel values of a plurality of pixels on either side of the noise region are copied only from the portion of its width. United States Patent Application Publication No.US2003/0090742, however, points out the problem of the unnaturalness of the resulting image obtained by simply copying an image adjacent to the noise region to a multi-valued gray image or color image.